内蒙古北山地区小黄山蛇绿岩地质特征

小黄山蛇绿岩产出于塔里木陆块东北缘,北山造山带东端,主要由全蛇纹石化橄榄岩、辉橄岩、辉石岩、辉长岩、辉绿岩及基性火山岩等组成。其中,蛇纹石化橄榄岩属变质橄榄岩,辉石岩、辉长岩为堆晶杂岩,其物质组成和空间展布反映出该蛇绿岩具有构造蛇绿混杂岩的一般特征。基性火山岩具弱亏损的稀土特征,同时微量元素显示岛弧拉斑玄武岩的特点,综合特征反映来源于富集型地幔源区,具有岛弧拉斑玄武岩与N-MORB型的双重特点。依据本区蛇绿岩的产出规模、岩石组合及地球化学特征分析,为弧后扩张时的产物,形成时代为晚寒武—早奥陶世。后期至少经历了4期以上构造变形变质作用的叠加改造,于晚泥盆世运移至地表。

The Geological Features of Ophiolites of Xiaohuangshan in Beishan Area,Inner Mongolia

Xiaohuangshan ophiolites outcropps in active continental margin,a great fault zone during the Early Paleozoic Era in nort heastern edge of Talimud land mass.The ophiolite was mainly composed of serpent inite,peridotite,pyroxenite,gabbro,diabase and limest one,the features of major elements and REEof basic volcanic rocks were similar to the OIT,and the features of trace elements were similar to the IAT.It had the general characteristics of tectonic ophiolite mixtite.According to the out cropping scale and the rock-group,the forming tectonic environment showed that it was the out come of island arc spreading, and formed during late Cambrian Epoch-early Ordo vician Epoch.It was later superimposed and reconstructed during at least 4 age deformation-metamorphism,and moved to the earth's surface at late Devonian.